(1) Field Of The Invention
This invention relates to the use of antireflection coating materials in the patterning of layers of reflective material and more particularly to the use of a layer of antireflection coating material sandwiched between two layers of photoresist.
(2) Description Of The Related Art
In the manufacture of semiconductor integrated circuits a layer of photoresist is frequently used to pattern metal layers. The photoresist is selectively exposed to form a mask from the photoresist layer. Reflections from the reflective metal layer can cause standing waves which deteriorate the accuracy of the pattern transferred to the layer of photoresist and consequently to the metal layer. Anti reflection coating materials are frequently used to avoid this problem.
U.S. Pat. No. 5,330,883 to Garza describes the use of an antireflection coating layer on top of the photoresist layer to define critical dimensions.
U.S. Pat. No. 5,449,639 to Wei et al. describes the use of an antireflection coating layer between the metal layer and the photoresist layer to avoid the problem of reflections.
U.S. Pat. No. 5,286,608 to Koh describes the use of titanium oxide as an antireflection coating layer between the metal layer and the photoresist layer to avoid the problem of reflections.
U.S. Pat. No. 5,308,742 to Ta describes the use of an organic polymer beneath the photoresist as an antireflection coating material.
The present invention describes the use of a layer of antireflection coating material between two layers of photoresist to control reflections and provide a planar surface on which to expose the pattern to be transferred. The bottom photoresist layer planarizes the surface of the wafer. The antireflection coating layer avoids the problem of reflections when the top photoresist layer, formed over the layer of antireflection coating material, is selectively exposed.